Eccentric oscillating gear device and assembling method for crankshaft in eccentric oscillating gear device

ABSTRACT

An eccentric oscillating gear device comprises a crankshaft having an eccentric portion, an externally toothed gear having external teeth and a through-hole in which the eccentric portion is inserted, an outer cylinder, and a carrier. The carrier rotatably supports the crankshaft. The outer cylinder has internal teeth meshed with the external teeth of the externally toothed gear. The eccentric oscillating gear device is provided with rotational phase adjusting section for setting an orientation of the crankshaft about an axis thereof, on the basis of orientations of the outer cylinder and the carrier about an axis thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an eccentric oscillating gear device, and a method of assembling a crankshaft in the eccentric oscillating gear device.

2. Description of the Related Art

Heretofore, there has been known an eccentric oscillating gear device disclosed in JP 2001-353684A. The eccentric oscillating gear device disclosed in JP 2001-353684A is designed such that an externally toothed gear is oscillatingly rotated interlockingly with a rotation of an eccentric body provided on a crankshaft, to allow an outer cylinder and a carrier to be relatively rotated with respect to each other. In this gear device, the outer cylinder is fixed to a first member of a robot, and the carrier is adapted to be relatively rotated at a given rotation ratio with respect to the outer cylinder, and fixed to a second member of the robot. This gear device is provided with a positioning pin for setting the carrier to a given orientation with respect to the second member of the robot.

Meanwhile, in an operation of assembling an eccentric oscillating gear device, generally, a crankshaft and an externally toothed gear are assembled to a carrier, and then the carrier is assembled to an outer cylinder. In this case, the crankshaft can be assembled to the carrier without any restriction in terms of an eccentric direction of an eccentric body of the crankshaft. However, depending on the eccentric direction of the assembled crankshaft, a rotational phase difference occurs in torsional rigidity of the gear device. This causes a problem that, in cases where the gear device is disassembled during maintenance or the like and then re-assembled, a phase of the torsional rigidity in a rotation direction is changed from that before the disassembling. Moreover, the gear device is free from restriction in terms of the eccentric direction. Thus, there is another problem that an individual difference in phase of the torsional rigidity in the rotation direction occurs between respective ones of a plurality of the gear devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an eccentric oscillating gear device capable of solving the above problems, and a method of assembling a crankshaft in the eccentric oscillating gear device.

More specifically, the present invention is directed to reducing a variation in phase of torsional rigidity of an eccentric oscillating gear device in a rotation direction.

According to one aspect of the present invention, there is provided an eccentric oscillating gear device for transmitting driving force while changing a rotation speed at a given rotation speed ratio between a first member and a second member. The gear device comprises a crankshaft having an eccentric portion, a gear member having a tooth portion and a through-hole in which the eccentric portion is inserted, a first cylindrical section adapted to be attachable to one of the first and second members, and a second cylindrical section adapted to be attachable to a remaining one of the first and second members. One of the first and second cylindrical sections rotatably supports the crankshaft, and a remaining one of the first and second cylindrical sections has a tooth portion meshed with the tooth portion of the gear member. The first and second cylindrical sections are adapted to be rotatable concentrically and relatively with respect to each other according to an oscillating movement of the gear member along with a rotation of the crankshaft. The eccentric oscillating gear device is provided with rotational phase adjusting section for setting an orientation of the crankshaft about an axis thereof, on the basis of orientations of the first and second cylindrical sections about an axis thereof.

According to another aspect of the present invention, there is provided a method of assembling a crankshaft in an eccentric oscillating gear device for transmitting driving force while changing a rotation speed at a given rotation speed ratio between a first member and a second member. The crankshaft assembling method comprises the steps of: assembling a crankshaft having an eccentric portion to a gear member; assembling the crankshaft to one of a first cylindrical section and a second cylindrical section; assembling the gear member to a remaining one of the first and second members which has a tooth portion; and combining the first and second cylindrical sections together. In the crankshaft assembling method, the step of assembling the crankshaft to one of a first cylindrical section and a second cylindrical section includes using rotational phase adjusting section to set an orientation of the crankshaft about an axis thereof, with respect to one of the first and second cylindrical sections, and the step of combining the first and second cylindrical sections together includes using the rotational phase adjusting section to set an orientation of the second cylindrical section about an axis thereof, with respect to the first cylindrical section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an eccentric oscillating gear device according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG. 1.

FIG. 3 is a view from the line III-III in FIG. 1.

FIG. 4 is a perspective view of a temporary locking pin.

FIGS. 5A to 5D are diagrams illustrating a rotational phase.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, the present invention will now be specifically described based on one embodiment thereof.

As illustrated in FIG. 1, an eccentric oscillating gear device 10 according to this embodiment comprises: an outer cylinder 12 serving as a first cylindrical section; a carrier 14 disposed inside the outer cylinder 12 to serve as a second cylindrical section adapted to be relatively rotatable with respect to the outer cylinder 12; an input shaft 16 adapted to generate a rotational driving force for rotating the carrier 14; and a speed reduction mechanism 18 adapted to rotate the carrier 14 at a rotation speed reduced at a given ratio with respect to a rotation speed of the input shaft 16. The gear device 10 is designed to transmit driving force while changing a rotation speed at a given rotation speed ratio, between a first arm 20 serving as a first member, and a second arm 38 serving as a second member. For example, the gear device 10 is configured as a speed reducer for use in an articulated joint for robot arms.

The outer cylinder 12 is formed in a cylindrical shape, and an inner peripheral surface of the outer cylinder 12 has a large number of pin grooves 12 c formed at even intervals in a circumferential direction thereof. As also illustrated in FIG. 2, a pin-shaped internal tooth 24 is fitted in each of the pin grooves 12 c. In other words, in this embodiment, the outer cylinder 12 serving as the first cylindrical section has internal teeth 24.

The outer cylinder 12 has an outer peripheral portion integrally provided with a flange 12 a. The flange 12 a has a plurality of bolt-insertion holes 12 b provided at even intervals in a circumferential direction thereof. In this embodiment, the bolt-insertion hole 12 b is provided in a number of eight. The outer cylinder 12 and the first arm 20 are fastened together by inserting a plurality of bolts 21 in respective ones of the bolt-insertion holes 12 b, and screwing the inserted bolts 21 with respective ones of a plurality of screw holes 20 c of the first arm 20. One of axially opposite ends (in FIG. 1, a right end) of the outer cylinder 12 is closed by the first arm 20. A motor 22 serving as a driving source is fixed to the first arm 20 which has a drive-shaft insertion hole 20 a formed to penetrate therethrough in a thickness direction thereof so as to allow a drive shaft 22 a of the motor 22 to be inserted thereinto.

The carrier 14 is supported by the outer cylinder 12 through a pair of main bearings 26 disposed in axially spaced-apart relation. Thus, the carrier 14 is adapted to be rotatable concentrically with the outer cylinder 12. In other words, the carrier 14 is adapted to be rotated about an axis O1 of the outer cylinder 12 and relatively with respect to the outer cylinder 12. Each of the main bearings 26 is composed of an angular ball bearing.

The carrier 14 comprises a circular disk-shaped end plate portion 30 serving as a first side portion, a circular disk-shaped base plate portion 32 serving as a second side portion, and a shaft portion 33 protrudingly provided on one surface of the base plate portion 32. The shaft portion 33 is integrally formed with the base plate portion 32. As illustrated in FIG. 2, the shaft portion 33 has a generally hexagonal shape in cross-section. In this embodiment, the shaft portion 33 is provided in a number of three, wherein the three shaft portions 33 are arranged at even intervals in a circumferential direction of the base plate portion 32. After a distal end face of the shaft portion 33 is brought into contact with the end plate portion 30, the shaft portion 33 is fastened to the end plate portion 30 by a bolt 34. In this state, a space having a given width in the axial direction is defined between the base plate portion 32 and the end plate portion 30.

The shaft portion 33 is provided with a bolt-fastening hole 33 a. The bolt 34 is inserted into a bolt-insertion hole 30 a of the end plate portion 30 from a side opposite to the shaft portion 33, and screwed with the bolt-fastening hole 33 a of the shaft portion 33. Further, a pin 36 is provided to extend between the shaft portion 33 and the end plate portion 30 so as to position the end plate portion 30 with respect to the base plate portion 32. Instead of being integrally formed with the base plate portion 32, the shaft portions 33 may be integrally formed with the end plate portion 30. In this case, the shaft portions 33 will be fastened to the base end portion 32.

The base end portion 32 is attached to the second arm 38 as a counterpart member, through an end face 32 c thereof on a side opposite to the end plate portion 30. The second arm 38 is formed with a plurality of bolt-insertion holes 38 a, and the base plate portion 32 has a plurality of fastening holes 32 d formed at positions corresponding to respective ones of the bolt-insertion holes 38 a. The second arm 38 and the base plate portion 32 are fastened together by inserting a plurality of bolts 37 in respective ones of the bolt-insertion holes 38 a of the second arm 38, and screwing the inserted bolts 37 with respective ones of the fastening holes 32 d of the base plate portion 32. Two or more (five) of the fastening holes 32 d are disposed at even intervals to form a fastening-hole group. The fastening-hole group is provided in a number of three, wherein the three fastening-hole groups are disposed about the axis O1 at even intervals (see FIG. 3).

As illustrated in FIG. 1, the end plate portion 30 and the base plate portion 32 are formed, respectively, with a through-hole 30 b and a through-hole 32 a each penetrating through a central region thereof in the axial direction. Each of the through-holes 30 b, 32 a is adapted to allow the input shaft 16 to be inserted thereinto. The input shaft 16 is inserted in the through-holes 30 b, 32 a and disposed coaxially with the outer cylinder 12.

The input shaft 16 has a base end coaxially joined to the drive shaft 22 a of the motor 22, and a distal end located within the through-hole 32 a of the base plate portion 32. The distal end of the input shaft 16 is integrally provided with a drive gear 42 composed of an externally toothed gear.

The speed reduction mechanism 18 comprises spur gears 44, crankshafts 46, and externally toothed gears (a first externally toothed gear 48 a and a second externally toothed gear 48 b) serving as gear members. Each of the first and second externally toothed gears 48 a, 48 b has external teeth meshed with the internal teeth of the outer cylinder 12. The spur gear 44 is splined to a base plate portion-side end of the crankshaft 46, and meshed with the drive gear 42 provided on the input shaft 16. Thus, driving force is transmitted to the crankshaft 46 through the spur gear 44, so that the crankshaft 46 is interlocked with a rotation of the input shaft 16.

The crankshaft 46 is disposed parallel to the input shaft 16. The crankshaft 46 is rotatably supported by the end plate portion 30 through a first crankshaft bearing 51, and rotatably supported by the base plate portion 32 through a second crankshaft bearing 52. In other words, the first crankshaft bearing 51 is disposed between the end plate portion 30 and the crankshaft 46, and the second crankshaft bearing 52 is disposed between the base plate portion 32 and the crankshaft 46. Each of the first and second crankshaft bearings 51, 52 is composed of a tapered roller bearing.

The end plate portion 30 and the base plate portion 32 are formed with a through-hole 30 c and a through-hole 32 b, respectively. The through-hole 30 c (32 b) is formed in a number of three, wherein the three through-holes 32 c (32 b) are arranged around the through-hole 30 b (32 a) at even intervals in a circumferential direction. The crankshaft 46 is provided in a number of three, wherein the three crankshafts 46 are disposed at even intervals in the circumferential direction (see FIG. 2), while penetrating through respective paired ones of the through-holes 30 c, 32 b.

The crankshaft 46 has a shaft body 46 c, and eccentric portions (a first eccentric portion 46 a and a second eccentric portion 46 b) integrally formed on the shaft body 46 c. The shaft body 46 c has a cross-sectionally circular shape, and each of the first and second eccentric portions 46 a, 46 b is eccentrically disposed with respect to a crankshaft axis O2 which is an axis of the shaft body 46 c. The first and second eccentric portions 46 a, 46 b are shifted in phase angle with respect to each other. Specifically, an eccentric direction of the first eccentric portion 46 a with respect to the crankshaft axis O2 and an eccentric direction of the second eccentric portion 46 b with respect to the crankshaft axis O2 are different from each other, and the respective phase angles of the first and second eccentric portions 46 a, 46 b are shifted in phase angle by 180 degrees. The three crankshafts 46 are assembled to allow respective eccentric directions of the first eccentric portions 46 a thereof to coincide with each other.

The first and second eccentric portions 46 a, 46 b are disposed between the first and second crankshaft bearings 51, 52 in axially adjacent relation to each other. The first eccentric portion 46 a is disposed adjacent to the first crankshaft bearing 51, and the second eccentric portion 46 b is disposed adjacent to the second crankshaft bearing 52.

Each of the first externally toothed gear 48 a and the second externally toothed gear 48 b is disposed within the space between the base plate portion 32 and the end plate portion 30. As also illustrated in FIG. 2, each of the first and second externally toothed gears 48 a, 48 b is formed with a first through-hole 48 c for allowing the input shaft 16 to penetrate therethrough, a second through-hole 48 d for allowing each of the shaft portions 33 to penetrate therethrough, and a third through-hole 48 e for allowing the first and second eccentric portions 46 a, 46 b of each of the crankshafts 46 to penetrate therethrough.

A roller bearing 55 is attached to each of the first and second eccentric portions 46 a, 46 b. In this state, the first eccentric portion 46 a is inserted in the third through-hole 48 e of the first externally toothed gear 48 a, and the second eccentric portion 46 b is inserted in the third through-hole 48 e of the second externally toothed gear 48 b. According to oscillating movements of the first and second eccentric portions 46 a, 46 b along with a rotation of the crankshaft 46, the first and second externally toothed gears 48 b are rotated while being meshed with the internal teeth 24 of the outer cylinder 12. In this embodiment, the gear device is designed such that the externally toothed gear is provided in a number of two. Alternatively, the gear device may be designed such that the externally toothed gear is provided in a number of one or in a number of three or more.

As illustrated in FIGS. 1 and 3, the through-hole 32 a and the three through-holes 32 b of the base plate portion 32 are communicated with each other, i.e., formed as a single through-hole, in the end face 32 c on the side opposite to the end plate portion 30. The spur gear 44 is located within the single through-hole at a position corresponding to each of the through-holes 32 b. Thus, when the base plate portion 32 is detached from the second arm 38, one principal surface 44 a of the spur gear 44 is exposed.

As illustrated in FIG. 3, the eccentric oscillating gear device 10 is provided with rotational phase adjusting means 58 for setting an orientation of the crankshaft 46 about the axis thereof, on the basis of orientations of the outer cylinder 12 and the carrier 14 about the axis thereof. The rotational phase adjusting means 58 comprises a first reference portion 58 a, a second reference portion 58 b and a third reference portion 58 c.

The first reference portion 58 a is provided in the outer cylinder 12 at a given position offset from the axis O1. In this embodiment, the first reference portion 58 a is composed of a hole formed in the flange 12 a of the outer cylinder 12. The first reference portion 58 a is provided in a number of one, wherein the one first reference portion 58 a is formed at a position to be aligned with a pin hole 20 b (see FIG. 1) of the first arm 20 when the flange 12 a is fastened to the first arm 20.

As mentioned above, the plurality of bolt-insertion holes 12 b are formed in the flange 12 a at even intervals in the circumferential direction of the flange 12 a. Thus, as long as each of the bolt-insertion holes 12 b is alignable with a respective one of the screw holes 20 c of the first arms 20, a circumferential orientation of the outer cylinder 12 can be variously set with respect to the first arm 20. However, based on providing the first reference portion 58 a, an orientation of the outer cylinder 12 about the axis O1 is fixed. Specifically, when the first reference portion 58 a is aligned with the pin hole 20 b formed in the first arm 20, the orientation of the outer cylinder 12 about the axis thereof is set to a given state with respect to the first arm 20. In this state, the outer cylinder 12 is fixedly attached to the first arm 20. Further, respective circumferential positions of the pin grooves 12 c with respect to the first arm 20 are also set.

A pin (position adjustment member) 60 (see FIG. 1) may be inserted to extend between the first reference portion 58 a and the pin hole 20 b of the first arm 20 so as to reliably perform the position adjustment. After completion of the position adjustment, the pin 60 may be detached.

Alternatively, the bolt-insertion holes 12 b formed in the flange 12 a in the circumferential direction thereof may be intentionally arranged at uneven intervals so as to allow the circumferential orientation of the outer cylinder 12 with respect to the first arm 20 to be set only in a single way. In this case, the bolt-insertion holes 12 b arranged at uneven intervals are used as the first reference portion 58 a.

The second reference portion 58 b is provided in the carrier 14 at a given position offset from the axis O1. In this embodiment, the second reference portion 58 b is composed of a hole formed in the end face 32 c of the base plate portion 32 of the carrier 14 on the side of the spur gears 44. More specifically, the second reference portion 58 b is provided in the end face 32 c of the base plate portion 32 which faces the second arm 38. The second reference portion 58 b is provided in a number of one, wherein the one second reference portion 58 b is formed at a position to be aligned with a pin hole 38 b (see FIG. 1) of the second arm 38 when the base plate portion 32 of the carrier 14 is fastened to the second arm 38.

As mentioned above, the plurality of fastening holes 32 d are formed in the base plate portions 32 in the circumferential direction thereof. Thus, as long as each of the fastening holes 32 d is alignable with a respective one of the bolt-insertion hole 38 a of the second arms 38, a circumferential orientation of the base plate portion 32 (carrier 14) can be variously set with respect to the second arm 38. However, based on providing the second reference portion 58 b, an orientation of the base plate portion 32 (carrier 14) about the axis thereof is specified.

When the second reference portion 58 b is aligned with the pin hole 38 b formed in the second arm 38, the orientation of the carrier 14 about the axis thereof is set to a given state with respect to the second arm 38. In this state, the carrier 14 is fixedly attached to the second arm 38. A temporary locking pin 62 (see FIGS. 3 and 4) may be inserted to extend between the second reference portion 58 b and the pin hole 38 b of the second arm 38 so as to reliably perform the position adjustment. After the position adjustment is completed by fixedly attaching the carrier 14 to the second arm 38, the temporary locking pin 62 may be detached.

Alternatively, the fastening holes 32 d formed in the base plate portion 32 in the circumferential direction thereof may be arranged in a specific pattern so as to allow the circumferential orientation of the base plate portion 32 (carrier 14) with respect to the second arm 38 to be set only in a single way. In this case, the fastening holes 32 d formed in the base plate portion 32 are used as the second reference portion 58 b.

The temporary locking pin 62 is formed as a three-forked pin which comprises a pin body 62 a formed in an arc shape, legs 62 b each extending from a respective one of opposite ends of the pin body 62 a, and a leg 62 c extending from an intermediate portion of the pin body 62 a. The leg 62 c extending from the intermediate portion is adapted to be insertable into the pin hole 38 b of the second arm 38 and the second reference portion 58 b of the carrier 14.

The third reference portion 58 c is provided in the spur gear 44 at a given position offset from the crankshaft axis O2. The third reference portion 58 c is provided in each of the three spur gears 44, wherein each of the third reference portions 58 c is set at a position where it has a given directional relation with the eccentric directions of the first and second eccentric portions 46 a, 46 b with respect to the crankshaft axis O2 of the crankshaft 46. In other words, each of the third reference portions 58 c has the same positional relationship with a corresponding one of the crankshaft axes O2. For example, the third reference portion 58 c may be formed in a direction coinciding with the eccentric direction of the second eccentric portion 46 b. Alternatively, as long as a positional relationship with each of the first and second eccentric portions 46 a, 46 b can be known, the third reference portion 58 c may be formed at any position.

The third reference portion 58 c is composed of a hole formed in the principal surface 44 a of the spur gear 44. The principal surface 44 a is exposed when the second arm 38 is detached. Specifically, the third reference portion 58 c is provided in the surface 44 a facing the second arm 38, as with the second reference portion 58 b provided in the end face 32 c of the base plate portion 32 of the carrier 14. One of the third reference portions 58 c is provided in a respective one of the spur gears 44. Each of the legs 62 b at the ends of the temporary locking pin 62 is adapted to be insertable into the third reference portion 58 c under a condition that the middle leg 62 c of the temporary locking pin 62 is inserted into the second reference portion 58 b of the carrier 14 as mentioned above.

The temporary locking pin 62 is not limited to the three-forked type. For example, a two-forked temporary locking pin 62 formed by omitting one of the end legs 62 b may be employed. In this case, one 62 c of two legs of the temporary locking pin 62 is inserted into the second reference portion 58 b, and the other leg 62 b is inserted into the third reference portion 58 c. Further, in this case, an additional temporary locking pin (illustration is omitted) may be used to, after positioning one of the three spur gears 44 (or crankshaft 46) with respect to the carrier 14, position the remaining two spur gears 44 (or two crankshafts 46) with respect to the positioned spur gear 44. In this case, the additional temporary locking pin may have a pin body 62 a formed in a triangular shape to allow three legs thereof to be simultaneously inserted into respective ones of the third reference portions 58 c.

Alternatively, a temporary locking pin (illustration is omitted) for positioning the second reference portion 58 b with respect to the second arm 38, and a temporary locking pin (illustration is omitted) for positioning the spur gear 44 (crankshaft 46) with respect to the carrier 14, may be formed as separate pins. In this case, the temporary locking pin for positioning the carrier 14 with respect to the second arm 38 may be composed of a rod-like pin. This rod-like pin may be used without being detached.

An operation of the eccentric oscillating gear device 10 according to this embodiment will be briefly described below. In the gear device 10, the input shaft 16 is driven by driving force of the motor 22, and, according to a resulting rotation of the input shaft 16, the spur gears 44 are rotated through the drive gear 42. Thus, each of the crankshafts 46 is rotated together with a corresponding one of the spur gears 44. Upon rotation of the crankshaft 46, according to an oscillating movement of the first eccentric portion 46 a, the first externally toothed gear 48 a is rotated while being meshed with the internal teeth 24. Further, according to an oscillating movement of the second eccentric portion 46 b, the second externally toothed gear 48 b is rotated while being meshed with the internal teeth 24. Thus, the carrier 14 having the shaft portions 33 each penetrating through the second through-holes 48 d of the first and second externally toothed gears 48 a, 48 b is rotated. Thus, the second arm 38 is relatively rotated with respect to the first arm 20. A rotation speed of the second arm 38 (carrier 14) has a value which is reduced at a given ratio with respect to a rotation speed input into the input shaft 16.

A reason for adjusting a rotational phase of the crankshaft 46 with respect to the outer cylinder 12 and the carrier 14 will be described below. FIG. 5A is a schematic diagram illustrating a positional relationship between respective ones of the first reference portion 58 a representing a reference point of the outer cylinder 12, the second reference portion 58 b representing a reference point of the carrier 14, and the third reference portion 58 c representing a reference point of the crankshaft 46. FIG. 5B schematically illustrates a position of the first reference portion 58 a on the first arm 20, and a position of the second reference portion 58 b on the second arm 38. FIGS. 5A and 5B illustrate a state when the outer cylinder 12, the carrier 14, and each of the crankshafts 46, are set to a given orientation about the axis O1 with respect to the first arm 20, a given orientation about the axis O1 with respect to the second arm 38, and a given orientation about the crankshaft axis O2, respectively. The solid line illustrated in FIG. 5C indicates torsional rigidity in a rotation direction when the carrier 14 in the above state is rotated about the axis O1 relatively with respect to the outer cylinder 12. The torsional rigidity is periodically changed. This is caused, for example, by a difference in circumferential weight of the carrier 14 about the axis O1 (e.g., a difference in weight between portions with and without the through-holes 30 c, 32 b), and a difference in weight of the crankshaft 46 about the crankshaft axis O2.

FIG. 5D illustrates a state when the second reference portion 58 b is displaced about the axis O1 from the position illustrated in FIG. 5A by about 30 degrees, and the third reference portion 58 c is rotated about the crankshaft axis O2 with respect to the carrier 14. For example, FIG. 5D may be assumed to be in a state when the gear device assembled as illustrated in FIG. 5A is disassembled for maintenance or the like and then re-assembled.

The solid line in FIG. 5C indicates torsional rigidity occurring when the carrier 14 is rotated from the position illustrated in FIG. 5A, and the broken line in FIG. 5C indicates torsional rigidity occurring when the carrier 14 is rotated from the position illustrated in FIG. 5D. As is clear from FIG. 5C, the torsional rigidity becomes different between when an initial setting is performed in a coupled state between the first and second arms 20, 38 illustrated in FIG. 5A and when the initial setting is performed in a coupled state between the first and second arms 20, 38 illustrated in FIG. 5D, even if the second arm 38 is located at the same position with respect to the first arm 20. Thus, if a rotational position adjustment between respective ones of the five components: the first arm 20, the second arm 38, the outer cylinder 12, the carrier 14 and the crankshaft 46, is not performed, the torsional rigidity at an initial set position is changed, so that it is necessary to perform a fine adjustment by means of teaching. Therefore, the rotational phase adjustment between respective ones of the five components can be performed to reduce a variation in torsional rigidity. In the above description, the reason for a variation in torsional rigidity has been explained by taking a variation in orientation of the carrier 14 with respect to the outer cylinder 12 as an example. However, the variation in torsional rigidity is also caused by a difference in orientation (eccentric direction) of the crankshaft 46 with respect to the outer cylinder 12, and by a difference in orientation (eccentric direction) of the crankshaft 46 with respect to the carrier 14. Thus, it is necessary to adjust orientations between respective ones of the outer cylinder 12, the carrier 14 and the crankshaft 46.

A process of assembling the crankshaft 46 in the eccentric oscillating gear device 10 will be briefly described below. In the process of assembling the crankshaft 46, the crankshaft 46 provided with the first and second eccentric portions 46 a, 46 b and integrated with the spur gear 44 is first assembled to the carrier 14. In this assembling step, the temporary locking pin 62 is inserted into the second reference portion 58 b and the third reference portion 58 c to set an orientation of the crankshaft 46 about the axis thereof with respect to the carrier 14. In conjunction with the setting of the orientation of the crankshaft 46 with respect to the carrier 14, the carrier 14 may be positioned with respect to the second arm 38. Alternatively, the carrier 14 may be subsequently positioned with respect to the second arm 38.

Then, the carrier 14 is assembled to the outer cylinder 12. In this assembling step, the first reference portion 58 a and the second reference portion 58 b are used to set an orientation of the carrier 14 about the axis thereof with respect to the outer cylinder 12. In this case, a positional relationship between the first reference portion 58 a and the second reference portion 58 b may be set to a given state on a visual basis, or using a two-forked temporary locking pin. Thus, an orientation of the crankshaft 46 about the crankshaft axis O2 is set on the basis of the orientations of the outer cylinder 12 and the carrier 14 about the axis O1. Then, the first arm 20 and the second arm 38 are fastened to the gear device using the pin 60 and the temporary locking pin 62. This makes it possible to establish a coupled state between the first and second arms 20, 38 under a condition that the orientation of the outer cylinder 12 with respect to the first arm 20, the orientation of the carrier 14 with respect to the second arm 38, and the orientation of the crankshaft 46 with respect to the outer cylinder 12 and the carrier 14, are set.

As described above, the eccentric oscillating gear device according to the above embodiment is capable of setting an orientation of the crankshaft 46 about the axis thereof, on the basis of orientations of the outer cylinder 12 and the carrier 14 about the axis thereof. Thus, when the outer cylinder 12 and the carrier 14 are attached, respectively, to the first arm 20 and the second arm 38, an orientation of the crankshaft 46 with respect to the first arm 20 and the second arm 38 can be set through the orientations of the outer cylinder 12 and the carrier 14. In other words, the orientation of the crankshaft 46 can be set using the rotational phase adjusting means. Thus, in cases where the gear device 10 is disassembled during maintenance or the like and then re-assembled, it becomes possible to prevent a phase of torsional rigidity in a rotation direction from being changed from that before the disassembling. Further, it becomes possible to prevent an individual difference in phase of the torsional rigidity in the rotation direction from occurring between respective ones of a plurality of the gear devices 10.

In the above embodiment, in an operation of assembling the crankshaft 46, the crankshaft 46 is assembled to allow the third reference portion 58 c to be set to a given position on the basis of the first reference portion 58 a and the second reference portion 58 b. Thus, the crankshaft 46 can be assembled such that an orientation thereof is set to a given state on the basis of the orientations of the outer cylinder 12 and the carrier 14 about the axis thereof.

In the above embodiment, during assembling of the crankshaft 46, a two-forked or three-forked temporary locking pin 62 is inserted to extend between the second reference portion 58 b and the third reference portion 58 c each composed of a hole, so that it becomes possible to reliably set an orientation of the crankshaft 46 with respect to the carrier 14. When the temporary locking pin 62 is subsequently detached, an eccentric oscillating gear device 10 can be provided in which the crankshaft 46 is assembled to the carrier 14 under a condition that the orientation of the crankshaft 46 is adjusted to a given state.

The present invention is not limited to the above embodiment, but various changes and modifications may be made therein without departing from the spirits and scope of the present invention. For example, although the above embodiment has been described based on an example where each of the first, second and third reference portions 58 a, 58 b, 58 c is composed of a hole, the present invention is not limited thereto. For example, at least one of the first, second and third reference portions 58 a, 58 b, 58 c may be composed of a mark discriminable from its surroundings, based on color, convexity or concavity.

Although the gear device according to the above embodiment is designed such that the third reference portion 58 c is provided in the spur gear 44, the present invention is not limited thereto. For example, the third reference portion 58 c may be provided in any other suitable portion viewable from the side of the second arm 38, such as an end face of the crankshaft 46 on the side of the second arm 38. Alternatively, the third reference portion 58 c may be provided in any other suitable portion viewable from the side of the first arm 20, such as an end face of the crankshaft 46 on the side of the first arm 20.

The gear device according to the above embodiment is designed such that the spur gear 44 is joined to the end of the crankshaft 46. Alternatively, the spur gear 44 may be disposed between the first eccentric portion 46 a and the second eccentric portion 46 b. In this case, the third reference portion 58 c may be provided in an end face of the crankshaft 46 or an end face of the second eccentric portion 46 b, as well as the one principal surface 44 a of the spur gear 44.

Although the gear device according to the above embodiment is designed such that the plurality of crankshafts 46 are arranged at positions offset from the axis O1 of the outer cylinder 12 at even intervals in the circumferential direction, the present invention is not limited thereto. For example, a so-called “center crank mechanism” may be employed in which a single crankshaft 46 is disposed in concentric relation with the outer cylinder 12 and the carrier 14. In this case, the third reference portion 58 c may be provided in a spur gear joined to the crankshaft 46. Further, in a structure where a spur gear is omitted, the third reference portion 58 c may be formed in a distal end face of the crankshaft 46.

In the above embodiment, in an operation of adjusting a rotational phase of the gear device 10, the temporary locking pin 62 is inserted into the second reference portion 58 b provided in the carrier 14, the third reference portion 58 c provided in the spur gear 44 and the pin hole 38 b provided in the second arm 38 to adjust the rotational phase. Alternatively, the rotational phase of the gear device 10 may be adjusted before the assembling to the second arm 38. For example, the temporary locking pin 62 is inserted into the second reference portion 58 b and the third reference portion 58 c from the side of one end (in FIG. 1, a left end) of the gear device 10 to adjust rotational phases of the carrier 14 and the crankshaft 46. In this state, the gear device 10 is assembled to the first arm 20 while adjusting the rotational phase thereof using the first reference portion 58 a. Then, the motor 22 is attached to the first arm 20 from the side of the other end (in FIG. 1, a right end) of the gear device 10, and the drive gear 42 of the input shaft 16 is meshed with the spur gear 44. Then, the motor is powered on to allow a reference rotational phase to be recognized by a servo lock function, a brake attached to the motor or the like, and fixed. Then, the temporary locking pin is detached from the gear device. Even if the temporary locking pin is detached, the carrier 14 and the crankshaft 46 are kept from rotating, for example, by the servo lock function. Finally, the gear device 10 is attached to the second arm 38 while adjusting respective positions of the second arm 38 and the first arm 20.

Although the above embodiment has been described based on a structure comprising the outer cylinder 12 provided with the internal teeth 24, and the first and second externally toothed gears 48 a, 48 b, the present invention is not limited thereto. For example, a structure may be employed which comprises a carrier provided with external teeth, and an internally toothed gear. This type of gear device is disclosed, for example, in JP 2000-065158A. Specifically, a carrier serving as the second cylindrical section is disposed coaxially with an outer cylinder serving as the first cylindrical section, while being partially located radially inward of the outer cylinder. The carrier has an outer peripheral surface provided with external teeth at a position radially inward of the outer cylinder. No tooth portion is provided on an inner peripheral surface of the outer cylinder. Further, a ring-shaped gear member having an inner peripheral surface provided with internal teeth meshable with the external teeth of the carrier is disposed between the carrier and the outer cylinder. The gear member is formed with a through-hole for allowing an eccentric portion of a crankshaft to be fitted therein. The crankshaft is rotated while receiving a torque from an input shaft directly or through a spur gear. The crankshaft is circumferentially provided in a number of two or more, wherein each of the crankshafts is rotatably supported by the outer cylinder, and the gear member is adapted to be oscillated according to a rotation of the crankshaft. Thus, the carrier having the external teeth meshed with the internal teeth of the gear member is rotated. Further, a second arm joined to the carrier can be relatively rotated with respect to a first arm joined to the outer cylinder. In this structure, the outer cylinder is formed with a first reference portion (e.g., a hole) for setting an orientation of the outer cylinder about an axis thereof with respect to the first arm, and the carrier is formed with a second reference portion (e.g., a hole) for setting an orientation of the carrier about an axis thereof with respect to the second arm. Further, the crankshaft or the spur gear is formed with a third reference portion (e.g., a hole) for setting an orientation of the crankshaft.

In the above embodiment, the outer cylinder is formed to serve as an example of the first cylindrical section, and the carrier is formed to serve as an example of the second cylindrical section. Alternatively, the carrier may be formed to serve as an example of the first cylindrical section, and the outer cylinder may be formed to serve as an example of the second cylindrical section.

An outline of the above embodiment will be described below.

(1) The eccentric oscillating gear device according to the above embodiment is provided with rotational phase adjusting means for setting an orientation of the crankshaft about an axis thereof, on the basis of orientations of the first and second cylindrical sections about an axis thereof. This makes it possible to set the orientation of the crankshaft about the axis thereof, on the basis of the orientations of the first and second cylindrical sections about the axis thereof. Thus, when the first cylindrical section and the second cylindrical section are attached, respectively, to a first member and a second member, an orientation of the crankshaft with respect to the first member and the second member can be set through the orientations of the first and second cylindrical sections. Thus, in cases where the gear device is disassembled during maintenance or the like and then re-assembled, it becomes possible to prevent a phase of torsional rigidity in a rotation direction from being changed from that before the disassembling. Further, it becomes possible to prevent an individual difference in phase of the torsional rigidity in the rotation direction from occurring between respective ones of a plurality of the gear devices.

(2) Preferably, the rotational phase adjusting means has a first reference portion provided in the first cylindrical section at a given position offset from the axis thereof, a second reference portion provided in the second cylindrical section at a given position offset from the axis thereof, and a third reference portion provided in the crankshaft or in a spur gear joined to the crankshaft, at a given position offset from the axis of the crankshaft.

According to this feature, in an operation of assembling the crankshaft, the crankshaft is assembled to allow the third reference portion to be set to a given position on the basis of the first reference portion and the second reference portion, so that the crankshaft can be assembled such that an orientation thereof is set to a given state on the basis of the orientations of the first and second cylindrical sections about the axis thereof.

(3) Each of the second and third reference portion may be formed as a hole.

According to this feature, during assembling of the crankshaft, a two-forked or three-forked temporary locking pin is inserted to extend between the second reference portion and the third reference portion each composed of a hole, so that it becomes possible to reliably set an orientation of the crankshaft with respect to the carrier. When the temporary locking pin is subsequently detached, an eccentric oscillating gear device can be provided in which the crankshaft is assembled to the first or second cylindrical section under a condition that the orientation of the crankshaft is adjusted to a given state.

(4) The crankshaft may be provided in a number of one. In this case, the one crankshaft may be disposed in concentric relation with respect to the first or second cylindrical section.

(5) The crankshaft may be provided in a number of two or more. In this case, the two or more crankshafts may be disposed about the axis of the first or second cylindrical section at even intervals.

(6) One of the first and second cylindrical sections may be a carrier, and a remaining one of the first and second cylindrical sections may be an outer cylinder having internal teeth. In this case, the gear member may be an externally toothed gear meshed with the internal teeth of the outer cylinder.

(7) One of the first and second cylindrical sections may be an outer cylinder, and a remaining one of the first and second cylindrical sections may be a carrier having external teeth. In this case, the gear member may be an internally toothed gear meshed with the external teeth of the carrier.

As mentioned above, the eccentric oscillating gear device according to the above embodiment is capable of reducing a variation in torsional rigidity in a rotation direction. 

1. An eccentric oscillating gear device for transmitting driving force while changing a rotation speed at a given rotation speed ratio between a first member and a second member, comprising: a crankshaft having an eccentric portion; a gear member having a tooth portion and a through-hole in which the eccentric portion is inserted; a first cylindrical section adapted to be attachable to one of the first and second members; and a second cylindrical section adapted to be attachable to a remaining one of the first and second members, wherein: one of the first and second cylindrical sections rotatably supports the crankshaft; a remaining one of the first and second cylindrical sections has a tooth portion meshed with the tooth portion of the gear member; the first and second cylindrical sections are adapted to be rotatable concentrically and relatively with respect to each other according to an oscillating movement of the gear member along with a rotation of the crankshaft, and wherein the eccentric oscillating gear device is provided with rotational phase adjusting section for setting an orientation of the crankshaft about an axis thereof, on the basis of orientations of the first and second cylindrical sections about an axis thereof.
 2. The eccentric oscillating gear device as defined in claim 1, wherein the rotational phase adjusting section has a first reference portion provided in the first cylindrical section at a given position offset from the axis thereof, a second reference portion provided in the second cylindrical section at a given position offset from the axis thereof, and a third reference portion provided in the crankshaft or in a spur gear joined to the crankshaft, at a given position offset from the axis of the crankshaft.
 3. The eccentric oscillating gear device as defined in claim 2, wherein each of the second and third reference portion is formed as a hole.
 4. The eccentric oscillating gear device as defined in claim 1, wherein the crankshaft is provided in a number of one, and is disposed in concentric relation with respect to the first or second cylindrical section.
 5. The eccentric oscillating gear device as defined in claim 1, wherein the crankshaft is provided in a number of two or more, and wherein the two or more crankshafts are disposed about the axis of the first or second cylindrical section at even intervals.
 6. The eccentric oscillating gear device as defined in claim 1, wherein: one of the first and second cylindrical sections is a carrier; a remaining one of the first and second cylindrical sections is an outer cylinder having internal teeth; and the gear member is an externally toothed gear meshed with the internal teeth of the outer cylinder.
 7. The eccentric oscillating gear device as defined in claim 1, wherein: one of the first and second cylindrical sections is an outer cylinder; a remaining one of the first and second cylindrical sections is a carrier having external teeth; and the gear member is an internally toothed gear meshed with the external teeth of the carrier.
 8. A method of assembling a crankshaft in an eccentric oscillating gear device for transmitting driving force while changing a rotation speed at a given rotation speed ratio between a first member and a second member, comprising the steps of: assembling a crankshaft having an eccentric portion to a gear member; assembling the crankshaft to one of a first cylindrical section and a second cylindrical section; assembling the gear member to a remaining one of the first and second members which has a tooth portion; and combining the first and second cylindrical sections together, wherein: the step of assembling the crankshaft to one of the first cylindrical section and the second cylindrical section includes using rotational phase adjusting section to set an orientation of the crankshaft about an axis thereof, with respect to one of the first and second cylindrical sections; and the step of combining the first and second cylindrical sections together includes using the rotational phase adjusting section to set an orientation of the second cylindrical section about an axis thereof, with respect to the first cylindrical section. 